ASK modulation is widely used in communication systems. For example, in an Electronic Toll Collection (ETC) system, a Road Side Unit (RSU) typically broadcasts ASK signals (such as a wake-up signal), and a demodulator in a Composite Password Card (CPC) carried by a vehicle typically receives and demodulates the ASK signals.
Conventionally, the demodulator may have inconsistent sensibility to ASK signals received from different directions, and may have high power consumption, which may affect life time of a disposable battery in the demodulator. Therefore, a new demodulator with consistent sensibility to ASK signals received from different directions and low power consumption becomes highly desirable.